JPH11183679A - Reactor shut-down device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structure of thermal elongation mechanism, to quickly increase the amount of thermal elongation when a reactor fails, and to easily drop a control rod. SOLUTION: A guide mechanism 34 with a support plate 34a and a cylindrical body 34b are mounted to the lower end of a thermally sensitive pipe 30 being used as the body of a thermal elongation mechanism. In the thermally sensitive pipe 30, a coil spring 32, a driving piston 32, and a driving shaft 31 are connected in series. The upper end of a coil spring 22 is connected to an upper extension rod 20. The outside of the driving shaft 31 is surrounded, and a bellows seal 26, whether the upper end is mounted to the driving piston 32 and the lower end is mounted to a guide mechanism 34, is provided. The guide mechanism 34 restrains the swing in a horizontal direction of the driving shaft 31. The lower end of the driving shaft 31 passing through the cylindrical body 34b of the guide mechanism 34 is screwed to a lower extension rod 21 via a stopper 35. The coil spring 22 is extended by a fixed amount using the stopper 35 for constantly maintaining the position of the driving piston 32, and the stopper 35 is rotated for adjusting the amount of drawing of the driving shaft 31. A plurality of guide pins 38 are provided on the side surface of the driving piston 32 for suppressing the swing of the driving piston 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor shutdown device having an improved thermal expansion type extension mechanism (hereinafter referred to as a thermal extension mechanism) installed in a fast breeder reactor.

[0002]

2. Description of the Related Art The core of a fast breeder reactor will be described with reference to FIG. FIG. 2 shows one block of the core. That is,
As shown in FIG. 2, the core of the fast breeder reactor has a plurality of fuel assemblies 2 in which a number of fuel pins 1 are bundled and housed in a hexagonal tubular wrapper tube and arranged in a honeycomb shape. A lower guide tube 3 having the same outer shape of the wrapper tube as the aggregate 2 is installed and configured.

A control rod body 4 is inserted into the lower guide tube 3, and a neutron absorber 5 called a control rod pin is incorporated inside the control rod body 4. Fuel assembly 2
The lower guide tube 3 has an entrance nozzle 6 at a lower portion, and the entrance nozzle 6 is inserted into a number of nozzles 8 provided on a core support plate 7 installed at a lower portion in the reactor vessel.

[0004] The core support plate 7 has a structure having a hollow high-pressure plenum 9, and a coolant having a higher pressure than that in the core is fed into the core support plate 7. A coolant inflow hole 10 is provided on a side surface of the entrance nozzle 6, and the coolant from the high-pressure plenum 9 flows through the coolant inflow hole 10, passes through a communication port 11 provided in the entrance nozzle 6, Aggregation 2
Flows into the trumpet tube and the lower guide tube 3.

[0005] An extension shaft 12 is connected to the upper portion of the control rod body 4, and the upper end thereof forms a grip portion 13. Grab part 13
Are connected by a connecting mechanism 15 provided at a lower end of an extension tube 14 of a control rod driving mechanism (not shown). During operation of the reactor, the control rod body 4 is pulled out of the core, and when the reactor is stopped, the control rod body 4 is inserted into the lower guide tube 3.

At the time of emergency stop of the reactor, the control rod body 4 is cut off at the position of the coupling mechanism 15, the control rod body 14 falls, and the dash ram 17 is inserted into the dash pot 16. When the dash ram 17 provided at the lower portion of the control rod body 4 enters the dash pot 16 provided at the bottom of the lower guide tube 3, the flow resistance of the coolant causes the shock at the time of drop of the control rod body 4 to be weakened and reduced. .

An upper guide tube 18 is provided outside the extension tube 14, and an umbrella-shaped introduction tube is provided at a lower end of the upper guide tube 18.
A coolant 19 passes through the fuel assembly 2 and guides the heated coolant to the extension shaft 12.

A conventionally proposed reactor shutdown device employs a thermal expansion mechanism as shown in FIGS. 3 (a) and 3 (b) without externally performing an artificial power suppression operation when the reactor power is abnormal. The control rod itself detects the temperature rise of the core and inserts the neutron absorbing part into the core to suppress the core power and improve the safety of the fast breeder reactor.

The thermal expansion mechanism corresponds to the portion A in FIG. 2. The structure of this thermal expansion mechanism will be described with reference to FIGS. 3 (a) and 3 (b). FIG. 3A shows the state of the thermal expansion mechanism during normal operation of the reactor, and FIG. 3B shows the operation state in a longitudinal sectional view.

In FIGS. 3A and 3B, the extension shaft 12 is divided into an upper extension rod 20 and a lower extension rod 21. A coil spring 22 is attached to the lower end surface of the upper extension rod 20, and the lower extension rod 21 is suspended from the coil spring 22 to maintain a constant gap.

A bellows seal 26 is provided so as to surround the outside of the coil spring 22, and the outside of the bellows seal 26 is
There is provided a temperature sensing portion 23 constituted by a double cylindrical temperature sensing member composed of an inner cylinder 23a and an outer cylinder 23b. The lower end between the inner cylinder 23a and the outer cylinder 23b is closed by an end plug 24,
The upper end of 23 is connected to the upper extension rod 20 to form an airtight structure.

A guide cylinder 25 is provided on the inner cylinder 23a side of the temperature sensing section 23 in order to suppress the swing of the lower extension rod 21 and has a guide function. The upper and lower ends of the bellows seal 26 are joined to the lower surfaces of the upper and lower ends of the upper extension rod 20 and the lower extension rod 21 and are kept airtight. The lower part of the upper extension rod 20 has a temperature sensor 23
Communication hole 27 that communicates the space between the bellows seal 26 and
Is formed, and a liquid metal 28 is sealed in a sealed space in the bellows seal 26.

A space between the inner cylinder 23a of the temperature sensing part 23 and the guide cylinder 25 is filled with a heat insulating member 29, so that the extension rods 20, 21 and the coil provided from the temperature sensing part 23 in the bellows seal 26 are provided. The structural member such as the spring 22 has a heat insulating function so that heat is not taken away.

Next, the operation of the extension mechanism of the reactor shutdown device will be described. During normal operation of the reactor, the temperature is in the state shown in FIG. 3A. However, when the temperature of the coolant rises and the temperature around the temperature sensing unit 23 increases when the reactor power is abnormal, the temperature sensing unit 23
Since it is a thin double cylinder composed of the outer cylinder 23a and the outer cylinder 23b, the temperature of the liquid metal 28 inside the cylinder also rises almost simultaneously.
When the temperature rises, the volume of the liquid metal 28 in the temperature sensing portion 23 expands, and flows into the bellows seal 26 from the temperature sensing portion 23 through the communication hole 27.

The liquid metal 28 in the bellows seal 26
The volume of the lower extension rod 21 increases as shown in FIG.
Is pushed down, the dash ram 17 of the control rod body 4 is inserted into the dash pot 16, and the control rod itself raises the temperature of the core without performing any artificial power suppression operation from the outside when the reactor power is abnormal. Can be detected to suppress the core power, which leads to an improvement in the safety of the fast reactor.

[0016]

In the above-mentioned conventional reactor shutdown device, the control rod extension shaft 12 is divided into two parts, and a thermal extension mechanism is provided in the divided part. Furnace power suppression function can be provided.

However, a further increase in the amount of control rod insertion is required, and the internal structure of the reactor vessel is limited in size. Therefore, without changing the external dimensions of the thermal expansion mechanism, the amount of control rod insertion can be increased. Need to be increased. In addition, since the elongation start temperature is set according to the amount of liquid metal 28 injected into the thermal elongation mechanism, there is a problem that once the liquid metal 28 is injected, the elongation start temperature cannot be easily changed. is there.

The extension operation of the thermal extension mechanism converts the volume increase due to the temperature rise of the liquid metal 28 inside the thermal extension mechanism main body into an insertion force.
Is larger than the internal volume of the thermal extension mechanism due to thermal expansion, the increased volume causes the lower extension rod 21 to extend.

As a means for increasing the extension amount, it is necessary to increase the injection amount of the liquid metal 28 injected into the inside of the thermal extension mechanism. However, the injection amount of the liquid metal 28 can be reduced without changing the dimensions of the thermal extension mechanism. There is a problem that it becomes very difficult to increase.

Further, since the structural members of the thermal expansion mechanism also undergo thermal expansion due to a rise in temperature, the volume inside the thermal expansion mechanism increases, and there is a problem that the amount of thermal expansion is absorbed and extension loss occurs. Furthermore, in order to improve the reliability of the thermal expansion mechanism, liquid metal
It is conceivable to provide an injection pipe for injecting 28 and install a cover at the sealing portion of the injection pipe, however, there is a problem that installation of the cover becomes difficult due to space restrictions.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can increase the amount of extension without changing the external dimensions of the thermal extension mechanism. Atoms that can increase the amount of liquid metal that greatly contributes to heat resistance, further improve heat transfer and easily adjust the elongation start temperature, make it easier to drop control rods, and improve the safety of the reactor Furnace shutdown device is provided.

[0022]

The invention according to claim 1 is
A control rod body accommodated in a guide tube installed in the core so as to be able to move up and down, an extension rod extending upward from an upper end of the control rod body, and a gripping portion provided on an upper portion of the extension rod are engaged. An extension pipe that suspends the control rod body, an upper extension rod and a lower extension rod that divide a part of the extension rod into two and constitute upper and lower end members of the divided portion, and an upper extension rod and a lower extension A temperature-sensitive pipe liquid-tightly interposed between the rod, a guide mechanism connected to a lower end of the temperature-sensitive pipe, a spring provided in the temperature-sensitive pipe and having an upper portion attached to the upper extension rod,
A drive piston connected to a lower part of the spring, an upper end connected to the drive piston, a lower end connected to the extension rod, and an upper end connected to the drive piston, and a lower end movable to the guide mechanism. A bellows seal connected to the drive shaft and surrounding the drive shaft; and a liquid metal sealed in the temperature-sensitive pipe outside the bellows seal.

The invention according to claim 2 is characterized in that the temperature-sensitive pipe is made of a corrosion-resistant low-thermal-expansion metal material, for example, tungsten, in a thin cylindrical shape. The invention according to claim 3 is characterized in that the guide mechanism includes a support plate having a through hole into which the drive shaft is inserted, and a cylindrical body suspended from the support plate.

The invention according to a fourth aspect is characterized in that the guide mechanism is sealingly joined to a lower portion of the temperature-sensitive pipe. The invention according to claim 5 is characterized in that a lower surface of the cylindrical body of the guide mechanism is detachably attached to an upper surface of a stopper which is screwed into a screw formed at a lower end of the drive shaft.

According to a sixth aspect of the present invention, the guide mechanism is provided with a liquid metal enclosing member having an injection pipe for injecting the liquid metal into the temperature-sensitive pipe, and a protective cap for covering the injection pipe. It is characterized by the following.

According to a seventh aspect of the present invention, the liquid metal injected from the liquid metal enclosure into the temperature-sensitive pipe is reduced by a temperature difference corresponding to an amount of expansion of deformation caused by an increase in pressure in the temperature-sensitive pipe. The injection is performed at a predetermined injection temperature.

In the invention according to claim 8, the liquid metal is injected at an injection temperature raised by a temperature difference corresponding to the pressure calculated from the weight of the spring and the suspended control rod and the amount of expansion caused by the pressure. It is characterized by the following.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a reactor shutdown device according to the present invention will be described with reference to FIGS. In this embodiment, the extension mechanism in the reactor shutdown device described with reference to FIGS. 3A and 3B is improved to reduce the amount of internal structure, increase the amount of liquid metal injected into the interior, and increase the extension amount. 1 (a) and 1 (b), FIG. 3 (a),
The same parts as in FIG. 2B are denoted by the same reference numerals, and the description of the core structure of the fast breeder reactor described with reference to FIG. 2 is omitted. FIG.
FIG. 1A shows a state during reactor operation, and FIG. 1B shows a state when the reactor power is abnormal.

In FIG. 1A, reference numeral 30 denotes a thin cylindrical long temperature-sensitive pipe. The upper end of the temperature-sensitive pipe 30 is connected to the upper extension rod 20, and the lower end of the temperature-sensitive pipe 30 is connected to a guide. Mechanism 34
Support plate 34a is sealed. The guide mechanism 34 includes a support plate 34a having a through hole 34c in the center, and a support plate 34a.
and a cylindrical body 34b extending downward from the through hole 34c and connected to the lower surface of the hole a.

The lower peripheral edge of the support plate 34a and the cylindrical body 34b
Liquid metal enclosure with a bottom that is liquid-tight over the lower outer peripheral surface of the
43 is installed. An injection pipe 39 communicating with the inside of the temperature-sensitive pipe 30 is connected to the lower surface of the support plate 34a, and a protective cap 40 surrounding the injection pipe 39 is detachably provided on the lower surface of the support plate 34a.

A coil spring 22 having a connecting portion 33 at the lower end face of the upper extension rod 20 and having an upper portion connected thereto, a driving piston 32 connected to the lower end portion of the coil spring 22, and a thermosensitive pipe 30.
It has a drive shaft 31 attached to the drive piston 32, and a bellows seal 26 surrounding the drive shaft 31.

The bellows seal 26 has a drive piston at the upper end.
32, the lower end is attached to the support plate 34a, and the upper and lower ends are respectively sealed and joined. A plurality of guide pins 38 are attached to both side surfaces of the drive piston 32 to suppress the swing of the drive piston 32. A bolt screw 36 is formed at the lower end of the drive shaft 31, and a nut-shaped stopper 35 or a nut 37 is screwed into the bolt-shaped screw 36. On the upper surface of the stopper 35, the lower end surface of the cylindrical portion 34b of the guide mechanism 34 is placed.

The drive shaft 31 is inserted through the through hole 34, and the screw 36 of the drive shaft 31 is screwed and connected to a screw for providing the lower extension rod 21. The inside of the temperature-sensitive pipe 30 has an airtight structure due to the above configuration, and the inside of the liquid metal
28 is enclosed. Liquid surface 41 of liquid metal 28 in thermosensitive pipe 30
The upper part has a space part.

The upper portion of the coil spring 22 is connected to the lower end of the upper extension rod 20 by providing a connecting portion 33.
Due to the resilience of 22, a drive force is applied to the drive shaft 31 to lift it upward. The lower end of the temperature-sensitive pipe 30 smoothly moves the drive shaft 31 up and down, and a guide mechanism 34 is sealed to seal the lower end of the temperature-sensitive pipe 30. With the above structure, the inside of the temperature-sensitive pipe 30 becomes an airtight structure, and the liquid metal 28 is sealed therein.

As described above, the stopper 35 is screwed into the lower end of the drive shaft 31, and the upper surface of the stopper 35 contacts the lower surface of the cylindrical body 34b of the guide mechanism 34, so that the drive shaft 31 can be maintained at a fixed position. Further, the stopper 35 can be replaced with a screw 36 and a nut 37 cut at the lower end of the drive shaft 31 as shown in the figure, and a function of adjusting the position of the drive shaft 31 by changing the screwing amount of the nut 37 is provided. be able to.
Since this adjustment function is performed outside the reactor vessel, the drive shaft 31
Can be easily changed.

A plurality of guide pins 38 are provided on the side surface of the drive piston 32, and the tips thereof are in contact with the inner wall surface of the temperature-sensitive pipe 30. At the time of elevating, the drive shaft 31 is moved to the guide mechanism 34,
The guide pin 38 is guided by the temperature-sensitive pipe, so that the vertical movement of the drive piston 32 can be smoothly performed while suppressing the lateral runout.

When the reactor power is abnormal, the structural members also undergo thermal expansion due to a rise in temperature.
This leads to an increase in the volume of the sealed space in which the liquid metal 28 is sealed. In the thermal expansion mechanism of the present invention, which converts the amount of thermal expansion of the liquid metal 28 into the expansion operation of the drive shaft 31, an increase in the volume of the space results in an expansion loss. Suppress volume increase. As the corrosion resistant low thermal expansion metal material, for example, tungsten is suitable.

The sealing of the liquid metal into the sealed space includes a method of using a liquid metal having a high melting point in a conventional structure, incorporating the liquid metal in a solid state, and returning the liquid metal to the liquid metal in a high temperature environment. Since the liquid metal is treated as a solid component, it is easy to inject the liquid metal into the sealed space. However, the liquid metal used is limited to those that are solid at room temperature. Therefore, in the present invention, since the liquid metal which is liquid even at room temperature is used, the guide mechanism 34 penetrates the support plate 34a as shown in FIG. A liquid metal sealing member 43 to which the injection pipe 39 can be attached is provided. Further, a protection cap 40 for protecting the injection pipe 39 after the liquid metal 28 is sealed in the temperature-sensitive pipe 30 is provided. As the liquid metal 28 to be injected, for example, the same metallic sodium (melting point: 97 ° C.) or sodium potassium alloy (melting point: −17 ° C.) as the reactor coolant is used.

Next, the operation of the reactor shutdown device according to the present invention will be described. FIG. 1A shows a normal operation of the reactor, and the control rod body 4 shown in FIG. 2 attached to the lower part of the extension rod 20 is pulled up by the coil spring 22 and is fixed at a predetermined position. It is. In this state, output control by the control rod drive mechanism is not affected. Further, at this time, in the sealed space of the temperature-sensitive pipe 30, there is a liquid surface 41 of the liquid metal, and the space 42 is in a vacuum state.

FIG. 1B shows the extended state. When the reactor power is abnormal, the coolant temperature rises and the temperature around the temperature-sensitive member rises. According to the second aspect of the present invention, since the temperature sensing pipe 30 is a thin cylindrical body made of a corrosion-resistant low-thermal-expansion metal material, for example, tungsten, the temperature of the liquid metal 28 inside the pipe rises almost simultaneously. Then, the volume of the liquid metal 28 sealed in the sealed space inside the temperature-sensitive pipe 30 expands, the volume of the internal space gradually decreases, and finally the space disappears.

Further, when the liquid metal thermally expands due to the temperature rise, as shown in FIG. 1 (b), a force exceeding the spring force of the coil spring 22 which lifts the control rod is generated and overcomes the spring force. The drive piston 32 will be pushed down.

When the temperature rise further continues, the thermal expansion of the liquid metal 28 also continues, so that the upper extension rod 20 is lowered and the control rod main body is inserted into the reactor core. Without performing the power suppression operation, the control rod itself can detect the temperature rise of the core and suppress the core power, thereby improving the safety of the fast reactor.

According to the first aspect of the present invention, the increase in volume due to the thermal expansion of the liquid metal is converted into the insertion force of the control rod, but setting the temperature at which the control rod is inserted is very important.
In the conventional setting method, the injection amount of the liquid metal is determined in consideration of the thermal expansion of the structural material and the amount of deformation of the structural material due to an increase in pressure in the sealed space due to the extension of the spring due to the extension operation.

According to the sixth aspect of the present invention, as a method of improving the accuracy of the temperature at which the elongating operation is started, the entire temperature-sensitive pipe is heated at the temperature at which the elongating operation is performed so that the thermal expansion of each part is completed and a stable state is maintained. Every other, from the injection pipe 39 to the temperature-sensitive pipe
Liquid metal 28 is injected into 30 and the entire temperature-sensitive pipe is crushed and sealed at operating temperature.

When the temperature of the temperature-sensitive pipe 30 is lower than the sealing temperature at this time, the drive shaft 31 is extended, and when the temperature is lowered, the liquid metal contracts more than at the time of sealing. Therefore, a vacuum space is formed in the temperature-sensitive pipe 30.

However, when the liquid metal is merely injected into the temperature-sensitive pipe 30, the internal pressure is at a normal pressure, and therefore, the deformation of the structural material due to the pressure increase in the temperature-sensitive pipe 30 during the actual extension is not included. The elongation start temperature shifts to the high temperature side by the amount of the deformation volume. Therefore, as in the invention according to claim 7 or 8, it is anticipated that the internal volume of the temperature-sensitive pipe will increase due to the deformation of the structural material at this time, and the injection temperature is corrected in consideration of the thermal expansion temperature of the liquid metal corresponding to the volume. .

Further, since there is a possibility that the elongation start temperature is deviated due to an error in the injection amount of the liquid metal, the screw-in amount of the nut-shaped stopper at the lower end of the drive shaft is adjusted as in the invention of claim 5, and The elongation start temperature can be adjusted to a higher side by extending the inner space and changing the internal space volume.

When the set elongation start temperature is changed within a certain range, it is possible to accurately set the target elongation start temperature by injecting liquid metal and adjusting the elongation axis in consideration of the above characteristics. Become. The sealing portion of the injection pipe for injecting the liquid metal, if the breakage or the like occurs, the liquid metal escapes to the outside and stops operating. Protection cap and protect the liquid metal from leaking out when the seal is broken.
Attach.

[0049]

According to the present invention, since the temperature rise of the coolant at the time of the reactor abnormality is utilized, the response to the temperature rise of the surroundings is quick, and the control rod is more securely inserted into the core than before. It can be inserted and can provide a large negative control rod reactivity to the core. Therefore, even if a scrum failure accident occurs, the reactor power is automatically attenuated, and the inherent safety of the reactor can be increased.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view showing a state of a reactor shutdown device according to a first embodiment of the present invention during a normal reactor operation,
(B) is a longitudinal sectional view showing a state at the time of an abnormal reactor power in (a).

FIG. 2 is a longitudinal sectional view showing a conventional reactor shutdown device.

3 (a) is a longitudinal sectional view showing a state during normal operation of the reactor in FIG. 2, and FIG. 3 (b) is a longitudinal sectional view showing a state when the reactor power is abnormal in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel pin, 2 ... Fuel assembly, 3 ... Lower guide tube, 4 ...
Control rod body, 5 neutron absorber, 6 entrance nozzle, 7 core support plate, 8 nozzle, 9 high-pressure plenum,
10 ... coolant inlet hole, 11 ... communication port, 12 ... extension shaft, 13 ... gripping part, 14 ... extension pipe, 15 ... coupling mechanism, 16 ... dash pot,
17… Dash ram, 18… Upper guide tube, 19… Introduction tube, 20…
Upper extension rod, 21 ... Lower extension rod, 22 ... Coil spring, 23 ... Temperature sensing part, 23a ... Inner cylinder, 23b ... Outer cylinder, 24 ... End plug, 25 ... Guide cylinder, 26 ... Bellows seal, 27 ... Communication hole , 28 ... liquid metal,
29: heat insulating material, 30: temperature-sensitive pipe, 31: drive shaft, 32: drive piston, 33: coupling part, 34: guide mechanism, 34a: support plate, 34b: cylindrical body, 34c: through hole, 35: stopper, 36…
Screws, 37 nuts, 38 guide pins, 39 injection pipes, 40
... Protective cap, 41 ... Liquid level, 42 ... Space, 43 ... Liquid metal injection member.

Claims (8)

[Claims] 1. A control rod body accommodated in a guide tube installed in a core so as to be able to move up and down, an extension rod extending upward from an upper end of the control rod body, and a grip provided on an upper portion of the extension rod. An extension pipe that engages with the part and suspends the control rod body; an upper extension rod and a lower extension rod that divide a part of the extension rod into two upper and lower members of the divided part; A temperature-sensitive pipe liquid-tightly interposed between the extension rod and the lower extension rod, a guide mechanism connected to a lower end of the temperature-sensitive pipe, and an upper part attached to the upper extension rod provided in the temperature-sensitive pipe. A spring, a drive piston connected to a lower portion of the spring, a drive shaft having an upper end connected to the drive piston and a lower end connected to the extension rod, and a drive shaft surrounding the outside of the drive shaft and having an upper end connected to the drive piston. Attached and lower end attached to the guide mechanism A reactor shutdown device comprising: a bellows seal; and a liquid metal sealed in the bellows seal and the temperature-sensitive pipe. 2. The reactor shutdown device according to claim 1, wherein said temperature-sensitive pipe is formed of a corrosion-resistant low-thermal-expansion metal material in a thin cylindrical shape. 3. The reactor shutdown according to claim 1, wherein the guide mechanism comprises a support plate having a through hole into which the drive shaft is inserted, and a cylinder suspended from a lower surface of the support plate. apparatus. 4. The reactor shutdown apparatus according to claim 3, wherein a support plate of said guide mechanism is formed by sealingly joining a lower end portion of said temperature-sensitive pipe. 5. A lower surface of a cylindrical body of the guide mechanism is mounted on an upper surface of a stopper screwed into a screw formed at a lower end of the drive shaft so as to be able to freely contact and separate therefrom.
Reactor shutdown device as described. 6. A liquid metal enclosing member having an injection pipe for injecting liquid metal into the temperature-sensitive pipe and a protective cap for covering the injection pipe is provided on a support plate of the guide mechanism. The reactor shutdown device according to claim 3, wherein 7. The liquid metal injected from the liquid metal enclosure into the temperature-sensitive pipe at an injection temperature reduced by a temperature difference corresponding to an amount of expansion of deformation caused by a pressure increase in the temperature-sensitive pipe. 7. The method according to claim 6, wherein
Reactor shutdown device as described. 8. The liquid metal is injected at an injection temperature which is increased by a temperature difference corresponding to a pressure calculated from the weight of the spring and the suspended control rod, and a corresponding expansion amount. Item 7. A reactor shutdown device according to item 6.